Everything about networking
So. Serializing IPv4 packets. Easy? Well, not exactly.
IPv4 was annoying to parse, because we had 3-bit integers, and 13-bit integers, and who knows what else. Serializing it is going to be exactly the same.
Alright. ALRIGHT. I know, we're all excited, but let's think about what we're doing again.
So we've managed to look at real network traffic and parse it completely. We've also taken some ICMP packets, parsed them, and then serialized them right back and we got the exact same result.
In the last part, we've finally parsed some IPv4 packets. We even found a way to filter only IPv4 packets that contain ICMP packets.
Hello and welcome to Part 11 of this series, wherein we finally use some of the code I prototyped way back when I was planning this series.
Where are we standing?
Now that we've found the best way to find the "default network interface"... what can we do with that interface?
Okay, I lied.
I'm deciding - right this instant - that using wmic is cheating too. Oh, it was fair game when we were learning about Windows, but we're past that now.
Let's set aside our sup project for a while.
Don't get me wrong - it's a perfectly fine project, and, were we simply rewriting "ping" for Windows in Rust, we could (almost) stop there.
Our ping API is simple, but it's also very limited:
pub fn ping(dest: ipv4::Addr) -> Result<(), String> // called as: ping(ipv4::Addr([8, 8, 8, 8])).unwrap();
We've just spent a lot of time abstracting over LoadLibrary, but we still have all the gory details of the Win32 ICMP API straight in our main.rs file! That won't do.
It's time to make sup, our own take on ping, use the Win32 APIs to send
an ICMP echo. Earlier we discovered that Windows's ping.exe used
IcmpSendEcho2Ex. But for our purposes, the simpler IcmpSendEcho will do
just fine.
So, how does ping.exe actually send a ping? It seems unrealistic that
ping.exe itself implements all the protocols involved in sending a ping.
So it must be calling some sort of library. Also, since it ends up
talking to the outside world via a NIC (network interface controller),
the kernel is probably involved at some point.
When I launched my Patreon, I vowed to explain how computers work. But in 2019, computers rarely work in isolation. So let's take the time to write a few articles about how computers talk to each other.